1. Field of the Invention
The present invention relates to ridge waveguide semiconductor lasers, and more particularly to a multi-layer structure and fabrication process for a 1300nm ridge waveguide structure.
A ridge waveguide laser is a semiconductor light-emitting device which includes a ridge-shaped layer on a semiconductor wafer. It is one of the fundamentally simplest and most reliable laser devices available today.
One such laser and its fabrication process has been described in an article "High Power Ridge-Waveguide AlGaAs GRINSCH Laser Diode" by C. Harder et al. (published in Electronics Letters, Sep. 25, 1986, Vol. 22, No. 20, pp. 1081-1082).
In the past, most of the efforts made in designing semiconductor lasers were directed to GaAs-system devices operating at a wavelength of about 0.8 um. However, particularly for communications applications, lasers emitting beams of longer wavelength (in the order of 1. 3 um) are also in great demand since they better match the transmission characteristics of the optical fiber links often used. An extensive survey on: such structures, including ridge waveguide lasers, and their performance is given in chapter 5 of a book entitled "Long Wavelength Semiconductor Lasers" by G. P. Agrawal and N. K. Dutta (Van Nostrand Reinhold Company, N.Y.).
Semiconductor lasers operating in this region of the infrared usually comprise regions of indium phosphide (InP) and of quaternary materials indium gallium arsenide phosphides (In.sub.x Ga.sub.1-x As.sub.y P.sub.1-y). By suitable choices of x and y it is possible to lattice-match the various regions while varying the band gaps of the materials. (Band gaps can be determined experimentally by, for example, photoluminescence.) Additionally, both indium phosphide and the quaternary materials can be doped to be p- or n-type as desired.
Ridge waveguide lasers have also been previously described, for example, in the following publications of Kaminow and his coworkers: Electronics Letters, 1979, vol. 15, pp. 763-765; Electronics Letters, 1981, vol. 17, pp. 318-320; Electronics Letters, 1983, vol. 19, pp. 877-879.